Most photosensing devices utilize photodiodes to convert light energy into electronic signals. Conventional photodiodes are p-n junctions or PIN structures that produce a photocurrent when light of a certain intensity strikes the photodiodes. The light energy in the form of photons of sufficient energy excites the electrons in the photodiodes to produce electron-hole pairs. The electron moves towards the conduction band from the valence band thereby producing a photocurrent.
Because most photosensing devices use this photocurrent to represent the intensity of light impinging on the photodiodes, the photosensing devices are vulnerable to high light intensity which may saturate the output signal of photosensing devices, and low light intensity which may induce too little photocurrent and reset circuitry is often needed to reset the photodiode. Therefore there is room for improvement in the art.